Psychological studies of cognitive development are often conducted without regard for the interplay between the cognitive activities of individuals and the cultural histories of communities. In my talk, I illustrate a heuristic research framework that illuminates this interplay through studies drawn from a program of work conducted in a remote Mountain Ok community in Papua New Guinea, the Oksapmin. Traditionally, the Oksapmin like their neighboring groups use a 27-body part counting system to represent quantity. Over three periods of fieldwork that stretch 23 years, I trace the shifting organization of the system and the shifting functions in serves as it is reproduced and altered in collective practices of daily life. Though the focus of the talk is on the Oksapmin case, I point to ways that the framework is useful for understanding the dynamics of culture-cognition relations more generally.